1. Field of the Invention
The present invention relates to an inkjet recording method, an inkjet recording device, and a recorded material.
2. Description of the Related Art
An inkjet recording system is a system in which ink droplets are jetted from very fine nozzles such that they are adsorbed to a recording member to thereby form characters and images on the recording member. This system has been widely used in recent years because images are formed in full color more easily in this inkjet recording system than in other recording systems and high resolution images are obtained using a device having a simple structure in this system.
Various characteristics are required for the ink used in this inkjet recording system. Particularly, jetting stability when the ink is jetted from the head is important because it affects image quality.
The characteristics of the ink are indicated by material properties such as viscosity and surface tension. The image qualities and wettability of the ink can be controlled by controlling these material properties.
When an ink droplet is ejected, a new ink meniscus is formed at the discharge port simultaneously when the ink droplet is ejected. In this case, the surface tension of the ink is different in different stages, for example, when the meniscus starts forming at the discharge port, just before the ink is ejected, at the moment the ink is ejected, when the ink is flying, at the moment the ink is landed onto a recording member, and when the ink penetrates into a recording member. Particularly, the surface tension of the ink under the condition (when a new meniscus plane starts forming and when the ink penetrates into a recording member such as paper) regarded as a static condition depressed in moving is largely different from that of the ink under the condition (the moment the ink is ejected) regarded as a dynamic condition accelerated in moving. For this, it is necessary to consider not only the static surface tension but also dynamic surface tension when evaluating the characteristics of inkjet recording ink.
Generally, the static surface tension affects the penetrability of ink into a recording member and is therefore preferably lower, whereas the dynamic surface tension affects discharge stability and is therefore preferably higher. It has been already known that these surface tensions can be controlled by the ratios of, for example, a surfactant and humectant to be added in ink.
JP-2011-062821-A discloses a method of forming a waveform to form droplets having different sizes from one driving waveform for the purposes of preventing the occurrence of droplet bending of the droplets even under the condition in which the nozzles are degraded and also, more shortening the length of a waveform than that of a conventional one in a droplet ejecting device which generates liquid droplets having a plurality of different sizes from one waveform structure. JP-2011-062821-A also discloses a waveform structure differentiating the shape of a discharge pulse generated from a driving pulse duplicatively used corresponding to the size of the droplet. This invention is similar to the present invention in the point that it has a waveform element which expands the pressure liquid chamber in at least two stages to draw a meniscus in the pressure chamber. However, no study is made concerning the properties of ink, posing the problem that discharge stability cannot be secured by the properties of ink.
Also, JP-2008-239964-A discloses an inkjet recording ink set and recording method in which the relation between the surface tensions of a black ink and other color inks is defined to suppress white haze and bleeding at the boundary between different colors when the black ink and color inks which are different in penetrability are used.
However, there is no evidence of studies concerning the influences of both dynamic surface tension and static surface tension and also, nothing refers to discharge stability. Therefore, the problem concerning the securing of discharge stability is unsolved.